1. Field of the Invention
The present invention relates to an audio signal playback apparatus, and more particularly, to an earphone.
2. Description of the Prior Art
Multi-media devices, such as computers, mobile phones, or MP3 players, are commonly used devices that can provide a wide variety of multi-media entertainment. Earphones are often used in conjunction with these devices for convenience, particularly when the devices are portable.
Commercial headsets are available as mono headsets and stereo headsets. The former is usually applied in cell phones to provide hands-free capability. When the headsets are connected to Bluetooth modules, users can answer telephone calls through the headsets directly. In general, mono headsets are designed to be small and delicate. Mono headsets, however, are not suitable for listening to stereo music, not only because they comprise only one earphone but also because the sound is limited to the vocal frequency range (300 Hz˜3 KHz).
Stereo headsets are mostly used when users wish to listen to music as they have two earphones for providing stereo sound. There are three types of stereo headsets: head-wear headsets, neck-wear headsets, and ear-wear headsets, and they generally comprise a right earphone and a left earphone, wherein the right earphone is unable to be worn on the left ear and vice versa.
Moreover, one earphone of the stereo headset may have the function of Bluetooth. This is very convenient, as a user does not need to disconnect the stereo headset to answer the phone. The Bluetooth earphone is generally designed for only one ear according to the structure of the ear, and comprises a body and an ear hook that is only suitable for that particular ear; however, wearing the earphone in the same ear for a long time is uncomfortable. In addition, there is a need to adjust the distance between the ear hook and the ear according to the user's preference. The conventional techniques available are unable to overcome the above-mentioned problems.